The study's findings suggest that breastfeeding may be no more beneficial than bottle-feeding for all but one of these 11 benefits in children aged four to 14.

Among siblings fed differently, the study found “little empirical evidence to support the notion that breastfeeding results in improved health and wellbeing for children between four and 14 years of age.”

Based on its results, the currently presumed impact of breastfeeding on child wellbeing and health “may be overstated," said the study.

Breastfed may “be worse off”

OSU researchers used data from the 1979 cohort of the National Longitudinal Survey of Youth (NLSY), a national sample of men and women between the ages of 14 and 22, and results from NLSY surveys between 1986 and 2010 of children born to women in the 1979 cohort.

The children were between the age of four and 14 at the time.

Three sample groups were analyzed: 8,327 children, 7319 siblings, and 1,773 discordant sibling pairs (children from 665 survey families in which at least one child was breastfed and at least one bottle-fed).

The analysis of adults and their children across families (between-family) suggested that breastfeeding resulted in better outcomes than bottle-feeding in 10 of the 11 examined measures.

Results from the study’s analysis of siblings fed differently within the same families (within-family), however, led the OSU researchers to “reconsider the notion that breastfeeding unequivocally results in improved childhood health and wellbeing.”

“When comparing results from between- to within-family estimates, coefficients for 10 of the 11 outcomes are substantially attenuated toward zero and none reach statistical significance,” said the study.

“Moreover, the signs of some of the regression coefficients actually change direction suggesting that for some outcomes, breastfed children may actually be worse off than children who were not breastfed.”

Of the 11 outcomes measured, asthma was branded an “outlier” by OSU researchers, as it was found across the board to be associated more with breastfeeding than with bottle-feeding.

“Let’s be more realistic”

Commenting, lead author of the report and assistant professor of sociology at OSU, Cynthia Colen, said that the findings could have potential implications for health policy.

“If breastfeeding doesn’t have the impact that we think will have on long-term childhood outcomes, then even though it is very import in the short-term we really need to focus on other things,” she said.

“We need to look at school quality, adequate housing and the type of employment parents have when their kids are growing up.”

“We need to take a much more careful look at what happens past that first year of life and understand that breast-feeding might be very difficult, even untenable, for certain groups of women. Rather than placing the blame at their feet, let’s be more realistic about what breastfeeding does and doesn’t do," she said.

"Its always difficult to prove ‘benefits of breastfeeding’ because from a methodological point of view studying the benefits of breastfeeding is always going to be flawed by the huge number of known and unknown confounders," said Rundall.

"But it should go without saying that breastfeeding should be protected, promoted and supported because it is part of our physiology, irrespective of whether it can be shown to be associated with this or that health outcome."